GE EntelliGuard G Application Manual page 51

Section 6. Application Data
4.9, the circuit breaker's rating, 100kA, must be
multiplied by 2.18/2.46 (from Table 6.1). The ratio is
.89. Hence, the circuit breaker must be considered
as if it is only rated for 89,000A. The UL 489 100kA
rated circuit breaker is not suitable for the applica-
tion because its de-rated 89kA rating is below the
available fault current of 92kA.
Consider an equivalent UL 1066 circuit breaker
tested at an X/R ratio of 6.6. The UL 1066 circuit
breaker must be de-rated by 2.31/2.46, which yields
0.94. The UL 1066 circuit breaker is then de-rated to
0.94 times 100kA. The UL 1066 circuit breaker is
rated higher than the available fault current of 92kA
and hence could be considered for the application.
Withstand Ratings, Selective Adjustable-, RELT-
and Override-Instantaneous Protection
Instantaneous adjustment capability for any circuit
breaker is intrinsically connected to the circuit
breaker's withstand rating and the trip system's
sensing methods. In the case of the EntelliGuard G
family of circuit breakers, high withstand ratings
allow for a broad range of instantaneous trip
options. The trip system relies on high accuracy
air core sensors not encumbered by the saturation
concerns associated with iron core sensors used
in many other trip systems. This allows the
EntelliGuard trip system to take full advantage of
the circuit breaker's withstand rating, providing
adjustable settings and full selectivity right up to the
circuit breaker's high withstand level. EntelliGuard
G circuit breakers, in conjunction with EntelliGuard
TU trip units with GE's unique "selective instanta-
neous" algorithm, allow selectivity capability as
high as 100kA with instantaneous on, and set at
surprisingly low values. The EntelliGuard family
of devices provides multiple solutions for your
selectivity and protection problems.
Low Voltage Power Circuit Breakers (LVPCBs) listed
to UL 1066 have defined fault current withstand
currents. EntelliGuard G UL 489 Insulated Case
Circuit Breakers also have substantial withstand
ratings. The stated withstand current (Icw) allows
the instantaneous protection of LVPCBs to be
turned off or set at very high values, and it's what
allows the short time bands of both types of cir-
cuit breakers to be delayed as much as 1/2 sec-
ond. EntelliGuard G UL 1066 LVPCBs with
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EntelliGuard TU trip units are available with two
different instantaneous adjustment ranges to take
full advantage of this capability.
The standard instantaneous adjustment range is
2-15X, adjustable in 1/2X increments on all UL 489
and UL 1066 circuit breakers. EntelliGuard TU trips
offer, for UL 1066 LVPCBs only, an extended
Instantaneous adjustment range that allows the
instantaneous pick up to be continuously adjusted
up to 30X, adjustable in 1X increments above 15X
the rating plug. The maximum adjustable pick up
setting is limited to approximately 95% of the circuit
breaker's withstand rating, or 30X trip plug current
rating, whichever is lower.
The EntelliGuard G's wide range of instantaneous
adjustability allows for maximum flexibility in pro-
viding the settings that are required for selectivity
or for optimum protection. Its capability is limited
by its withstand rating and the instantaneous
override. An instantaneous override is used in some
circuit breakers to ensure that, if a fault exceeds
the circuit breakers withstand capability, the circuit
breaker trips quickly. In all UL 489 EntelliGuard
circuit breakers, the override protection is
designed such that selectivity up to 100% of the
stated circuit breaker's withstand rating is possible.
In UL 1066 LVPCBs, maximum selective capability
is achieved by using the adjustable instantaneous
algorithm, even if it is set at maximum. When the
adjustable instantaneous is enabled, regardless of
setting, the override protection is set so that it will not
trip for faults below the circuit breaker's withstand
rating. If the adjustable instantaneous is disabled
(turned off), then the override automatically adjusts
downward by approximately 9%. This lowers the
maximum selective capability to 91% of the circuit
breaker's withstand rating. The EntelliGuard G LVPCB
may be selective up to the full withstand current with
adjustable instantaneous on and 91% of withstand
rating with adjustable instantaneous off.
The EntelliGuard TU trip unit also offers a second
adjustable instantaneous trip called the Reduced
Energy Let-Through (RELT) instantaneous pick up.
This trip offers a faster algorithm suitable for
application as alternate instantaneous pick up
setting for temporary use when faster and more
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